Training method and difficulty modulate electrophysiological correlates of visual perceptual learning.

The present study focused on the influence of training methods and task difficulty on event-related potentials (ERPs) at early and later visual perceptual learning (VPL) on a coherent motion identification task. Sixty participants were randomly divided into four groups for training with an adaptive stimulus (staircase group) and three constant stimuli (moderate, easy and difficult intensity groups). Visual performance improved in the staircase and moderate training groups but not in the easy or difficult training groups. ERP results revealed a decreased P1 amplitude in all groups. Additionally, staircase training increased the frontal P2 amplitude; accordingly, moderate constant stimulus training reduced the frontal P2 amplitude and increased the frontal N2 amplitude. Importantly, the change in frontal P2 amplitude was correlated with improved performance, indicating the involvement of cortices responsible for higher-order cognitive processes in VPL. Additionally, the difference in frontal P2 amplitude changes suggests the modulation of training methods (adaptive and consistent) on the role of attention in VPL. Furthermore, although behavior changes were not observed, the brains in the easy and difficult groups still presented different ERP changes. In summary, the results provide electrophysiological evidence for the modulation of training methods and task difficulty in VPL-related neuroplasticity.